1. Field of the Invention
This invention relates to a metering cap for the metered combination of two flowable components, which can be indirectly or directly placed on a container of the main component which can be actively emptied and which has an aspirating or feed line and an outlet line.
2. Description of Prior Art
In commerce as well as in industry, there is an always recurring requirement of metering two flowable components in a defined ratio and combining them. This is most simply realized industrially in that both components are volumetrically conveyed independently of each other and combined, and are only mixed at the place where they are brought together. This system is elaborate, because it requires two conveying devices acting independently of each other, which must be matched to each other by special controls for obtaining the appropriate mixture ratio. Such mixing systems are extremely unsuited for commercial applications or for applications requiring a high degree of mobility. Accordingly, it is necessary to improvise by first bringing the two components to be mixed together in a special container in the desired proportions, then to mix them and to fill them into a special dispenser. This is elaborate and unpleasant in handling, leading to considerable soiling and unavoidable losses of material.
With mixtures of two flowable components which are intended to be metered at approximately the same proportions and brought together, the two components are supplied in cartridges and the contents of both cartridges are simultaneously squeezed out in a single pressing device.
In connection with the present invention it is desired to make use of the known, commercially available cartridges and to use the also commercially known pressing devices. It is accordingly presumed that the quantitatively larger main component is available in a container which can be actively emptied.
A particularly serious problem arises in cases where the media to be mixed are very viscous. Given this premise, this results in the requirement that the metering cap must be laid out in accordance with flow technology in such a way that the smallest possible flow resistance occurs, and it must be possible to manufacture the metering cap with the fewest possible plastic parts.
The general idea to employ two pumps for mixing two media, both respectively causing a volumetric conveyance of the media to be mixed and to connect them mechanically, as a result of which a predetermined mixture ratio results, is taught by French Patent Publication FR-A-2 313 971. In this case, both media are present under pressure. The volumetrically metered components are conducted through appropriate lines into a separate high-pressure mixing chamber, conveyed outside of the pump and are there mixed together by a separately driven mixer.
Such an arrangement cannot be realized as a cap on a cartridge which can be squeezed out and is too expensive.
In contrast thereto, European Patent Publication EP-A-022,179 discloses a metering device with two pumps enclosed in a housing. The main medium drives a turbine-like hydraulic motor which acts on a piston pump which supplies an admixing component to the main component. The system is suited for fluid media, however, the hydraulic motor only permits inexact volumetric metering.
However, the mixing device in accordance with U.S. Pat. No. 3,054,417 operates precisely. Three pumps are used here. The main component is supplied under pressure and drives a volumetrically operating pump which drives two pumps for the admixing component by a gear. Here the first pump is used for building up pressure and it has a bypass in which a pressure valve is disposed. The second pump operates as a pure metering pump. If necessary, the pressure build-up pump can be provided with a separate drive motor. Mixing only takes place in the outlet line. There is no mixing chamber. Instead, in this case the flow of the main component is straight in order to achieve the highest possible conveying output. The device is complex and cannot be made of plastic at a reasonable price.
But U.S. Pat. No. 5,012,837 discloses a metering device of simple construction. The main component is present under pressure at a two-bladed metering pump operated as a hydraulic motor. It drives the shaft of a parallel disposed gear pump for the admixing component. Admixing is very exact and also permits low admixture ratios of 1:100. However, the device does not include a mixing unit. Both components are supplied separately and conveyed on separately. Thus, there is no mixing chamber. Both components are supplied and removed on the same side of the housing, which results in enormous flow resistances with viscous components.